1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

//! Common handling of keyboard input and state management for text input controls

use std::borrow::ToOwned;
use std::cmp::min;
use std::default::Default;
use std::ops::{Add, AddAssign, Range};
use std::usize;

use keyboard_types::{Key, KeyState, Modifiers, ShortcutMatcher};
use unicode_segmentation::UnicodeSegmentation;

use crate::clipboard_provider::ClipboardProvider;
use crate::dom::bindings::str::DOMString;
use crate::dom::compositionevent::CompositionEvent;
use crate::dom::keyboardevent::KeyboardEvent;

#[derive(Clone, Copy, PartialEq)]
pub enum Selection {
    Selected,
    NotSelected,
}

#[derive(Clone, Copy, Debug, JSTraceable, MallocSizeOf, PartialEq)]
pub enum SelectionDirection {
    Forward,
    Backward,
    None,
}

#[derive(Clone, Copy, Debug, Eq, JSTraceable, MallocSizeOf, Ord, PartialEq, PartialOrd)]
pub struct UTF8Bytes(pub usize);

impl UTF8Bytes {
    pub fn zero() -> UTF8Bytes {
        UTF8Bytes(0)
    }

    pub fn one() -> UTF8Bytes {
        UTF8Bytes(1)
    }

    pub fn unwrap_range(byte_range: Range<UTF8Bytes>) -> Range<usize> {
        byte_range.start.0..byte_range.end.0
    }

    pub fn saturating_sub(self, other: UTF8Bytes) -> UTF8Bytes {
        if self > other {
            UTF8Bytes(self.0 - other.0)
        } else {
            UTF8Bytes::zero()
        }
    }
}

impl Add for UTF8Bytes {
    type Output = UTF8Bytes;

    fn add(self, other: UTF8Bytes) -> UTF8Bytes {
        UTF8Bytes(self.0 + other.0)
    }
}

impl AddAssign for UTF8Bytes {
    fn add_assign(&mut self, other: UTF8Bytes) {
        *self = UTF8Bytes(self.0 + other.0)
    }
}

trait StrExt {
    fn len_utf8(&self) -> UTF8Bytes;
}
impl StrExt for str {
    fn len_utf8(&self) -> UTF8Bytes {
        UTF8Bytes(self.len())
    }
}

#[derive(Clone, Copy, Debug, JSTraceable, MallocSizeOf, PartialEq, PartialOrd)]
pub struct UTF16CodeUnits(pub usize);

impl UTF16CodeUnits {
    pub fn zero() -> UTF16CodeUnits {
        UTF16CodeUnits(0)
    }

    pub fn one() -> UTF16CodeUnits {
        UTF16CodeUnits(1)
    }

    pub fn saturating_sub(self, other: UTF16CodeUnits) -> UTF16CodeUnits {
        if self > other {
            UTF16CodeUnits(self.0 - other.0)
        } else {
            UTF16CodeUnits::zero()
        }
    }
}

impl Add for UTF16CodeUnits {
    type Output = UTF16CodeUnits;

    fn add(self, other: UTF16CodeUnits) -> UTF16CodeUnits {
        UTF16CodeUnits(self.0 + other.0)
    }
}

impl AddAssign for UTF16CodeUnits {
    fn add_assign(&mut self, other: UTF16CodeUnits) {
        *self = UTF16CodeUnits(self.0 + other.0)
    }
}

impl From<DOMString> for SelectionDirection {
    fn from(direction: DOMString) -> SelectionDirection {
        match direction.as_ref() {
            "forward" => SelectionDirection::Forward,
            "backward" => SelectionDirection::Backward,
            _ => SelectionDirection::None,
        }
    }
}

impl From<SelectionDirection> for DOMString {
    fn from(direction: SelectionDirection) -> DOMString {
        match direction {
            SelectionDirection::Forward => DOMString::from("forward"),
            SelectionDirection::Backward => DOMString::from("backward"),
            SelectionDirection::None => DOMString::from("none"),
        }
    }
}

#[derive(Clone, Copy, Debug, JSTraceable, MallocSizeOf, PartialEq, PartialOrd)]
pub struct TextPoint {
    /// 0-based line number
    pub line: usize,
    /// 0-based column number in bytes
    pub index: UTF8Bytes,
}

impl TextPoint {
    /// Returns a TextPoint constrained to be a valid location within lines
    fn constrain_to(&self, lines: &[DOMString]) -> TextPoint {
        let line = min(self.line, lines.len() - 1);

        TextPoint {
            line,
            index: min(self.index, lines[line].len_utf8()),
        }
    }
}

#[derive(Clone, Copy, PartialEq)]
pub struct SelectionState {
    start: TextPoint,
    end: TextPoint,
    direction: SelectionDirection,
}

/// Encapsulated state for handling keyboard input in a single or multiline text input control.
#[derive(JSTraceable, MallocSizeOf)]
pub struct TextInput<T: ClipboardProvider> {
    /// Current text input content, split across lines without trailing '\n'
    lines: Vec<DOMString>,

    /// Current cursor input point
    edit_point: TextPoint,

    /// The current selection goes from the selection_origin until the edit_point. Note that the
    /// selection_origin may be after the edit_point, in the case of a backward selection.
    selection_origin: Option<TextPoint>,
    selection_direction: SelectionDirection,

    /// Is this a multiline input?
    multiline: bool,

    #[ignore_malloc_size_of = "Can't easily measure this generic type"]
    clipboard_provider: T,

    /// The maximum number of UTF-16 code units this text input is allowed to hold.
    ///
    /// <https://html.spec.whatwg.org/multipage/#attr-fe-maxlength>
    max_length: Option<UTF16CodeUnits>,
    min_length: Option<UTF16CodeUnits>,

    /// Was last change made by set_content?
    was_last_change_by_set_content: bool,
}

/// Resulting action to be taken by the owner of a text input that is handling an event.
pub enum KeyReaction {
    TriggerDefaultAction,
    DispatchInput,
    RedrawSelection,
    Nothing,
}

impl Default for TextPoint {
    fn default() -> TextPoint {
        TextPoint {
            line: 0,
            index: UTF8Bytes::zero(),
        }
    }
}

/// Control whether this control should allow multiple lines.
#[derive(Eq, PartialEq)]
pub enum Lines {
    Single,
    Multiple,
}

/// The direction in which to delete a character.
#[derive(Clone, Copy, Eq, PartialEq)]
pub enum Direction {
    Forward,
    Backward,
}

// Some shortcuts use Cmd on Mac and Control on other systems.
#[cfg(target_os = "macos")]
pub const CMD_OR_CONTROL: Modifiers = Modifiers::META;
#[cfg(not(target_os = "macos"))]
pub const CMD_OR_CONTROL: Modifiers = Modifiers::CONTROL;

/// The length in bytes of the first n characters in a UTF-8 string.
///
/// If the string has fewer than n characters, returns the length of the whole string.
/// If n is 0, returns 0
fn len_of_first_n_chars(text: &str, n: usize) -> UTF8Bytes {
    match text.char_indices().take(n).last() {
        Some((index, ch)) => UTF8Bytes(index + ch.len_utf8()),
        None => UTF8Bytes::zero(),
    }
}

/// The length in bytes of the first n code units in a string when encoded in UTF-16.
///
/// If the string is fewer than n code units, returns the length of the whole string.
fn len_of_first_n_code_units(text: &str, n: UTF16CodeUnits) -> UTF8Bytes {
    let mut utf8_len = UTF8Bytes::zero();
    let mut utf16_len = UTF16CodeUnits::zero();
    for c in text.chars() {
        utf16_len += UTF16CodeUnits(c.len_utf16());
        if utf16_len > n {
            break;
        }
        utf8_len += UTF8Bytes(c.len_utf8());
    }
    utf8_len
}

impl<T: ClipboardProvider> TextInput<T> {
    /// Instantiate a new text input control
    pub fn new(
        lines: Lines,
        initial: DOMString,
        clipboard_provider: T,
        max_length: Option<UTF16CodeUnits>,
        min_length: Option<UTF16CodeUnits>,
        selection_direction: SelectionDirection,
    ) -> TextInput<T> {
        let mut i = TextInput {
            lines: vec![],
            edit_point: Default::default(),
            selection_origin: None,
            multiline: lines == Lines::Multiple,
            clipboard_provider,
            max_length,
            min_length,
            selection_direction,
            was_last_change_by_set_content: true,
        };
        i.set_content(initial);
        i
    }

    pub fn edit_point(&self) -> TextPoint {
        self.edit_point
    }

    pub fn selection_origin(&self) -> Option<TextPoint> {
        self.selection_origin
    }

    /// The selection origin, or the edit point if there is no selection. Note that the selection
    /// origin may be after the edit point, in the case of a backward selection.
    pub fn selection_origin_or_edit_point(&self) -> TextPoint {
        self.selection_origin.unwrap_or(self.edit_point)
    }

    pub fn selection_direction(&self) -> SelectionDirection {
        self.selection_direction
    }

    pub fn set_max_length(&mut self, length: Option<UTF16CodeUnits>) {
        self.max_length = length;
    }

    pub fn set_min_length(&mut self, length: Option<UTF16CodeUnits>) {
        self.min_length = length;
    }

    /// Was last edit made by set_content?
    pub fn was_last_change_by_set_content(&self) -> bool {
        self.was_last_change_by_set_content
    }

    /// Remove a character at the current editing point
    pub fn delete_char(&mut self, dir: Direction) {
        if self.selection_origin.is_none() || self.selection_origin == Some(self.edit_point) {
            self.adjust_horizontal_by_one(dir, Selection::Selected);
        }
        self.replace_selection(DOMString::new());
    }

    /// Insert a character at the current editing point
    pub fn insert_char(&mut self, ch: char) {
        self.insert_string(ch.to_string());
    }

    /// Insert a string at the current editing point
    pub fn insert_string<S: Into<String>>(&mut self, s: S) {
        if self.selection_origin.is_none() {
            self.selection_origin = Some(self.edit_point);
        }
        self.replace_selection(DOMString::from(s.into()));
    }

    /// The start of the selection (or the edit point, if there is no selection). Always less than
    /// or equal to selection_end(), regardless of the selection direction.
    pub fn selection_start(&self) -> TextPoint {
        match self.selection_direction {
            SelectionDirection::None | SelectionDirection::Forward => {
                self.selection_origin_or_edit_point()
            },
            SelectionDirection::Backward => self.edit_point,
        }
    }

    /// The byte offset of the selection_start()
    pub fn selection_start_offset(&self) -> UTF8Bytes {
        self.text_point_to_offset(&self.selection_start())
    }

    /// The end of the selection (or the edit point, if there is no selection). Always greater
    /// than or equal to selection_start(), regardless of the selection direction.
    pub fn selection_end(&self) -> TextPoint {
        match self.selection_direction {
            SelectionDirection::None | SelectionDirection::Forward => self.edit_point,
            SelectionDirection::Backward => self.selection_origin_or_edit_point(),
        }
    }

    /// The byte offset of the selection_end()
    pub fn selection_end_offset(&self) -> UTF8Bytes {
        self.text_point_to_offset(&self.selection_end())
    }

    /// Whether or not there is an active selection (the selection may be zero-length)
    #[inline]
    pub fn has_selection(&self) -> bool {
        self.selection_origin.is_some()
    }

    /// Returns a tuple of (start, end) giving the bounds of the current selection. start is always
    /// less than or equal to end.
    pub fn sorted_selection_bounds(&self) -> (TextPoint, TextPoint) {
        (self.selection_start(), self.selection_end())
    }

    /// Return the selection range as byte offsets from the start of the content.
    ///
    /// If there is no selection, returns an empty range at the edit point.
    pub fn sorted_selection_offsets_range(&self) -> Range<UTF8Bytes> {
        self.selection_start_offset()..self.selection_end_offset()
    }

    /// The state of the current selection. Can be used to compare whether selection state has changed.
    pub fn selection_state(&self) -> SelectionState {
        SelectionState {
            start: self.selection_start(),
            end: self.selection_end(),
            direction: self.selection_direction,
        }
    }

    // Check that the selection is valid.
    fn assert_ok_selection(&self) {
        debug!(
            "edit_point: {:?}, selection_origin: {:?}, direction: {:?}",
            self.edit_point, self.selection_origin, self.selection_direction
        );
        if let Some(begin) = self.selection_origin {
            debug_assert!(begin.line < self.lines.len());
            debug_assert!(begin.index <= self.lines[begin.line].len_utf8());

            match self.selection_direction {
                SelectionDirection::None | SelectionDirection::Forward => {
                    debug_assert!(begin <= self.edit_point)
                },

                SelectionDirection::Backward => debug_assert!(self.edit_point <= begin),
            }
        }

        debug_assert!(self.edit_point.line < self.lines.len());
        debug_assert!(self.edit_point.index <= self.lines[self.edit_point.line].len_utf8());
    }

    pub fn get_selection_text(&self) -> Option<String> {
        let text = self.fold_selection_slices(String::new(), |s, slice| s.push_str(slice));
        if text.is_empty() {
            return None;
        }
        Some(text)
    }

    /// The length of the selected text in UTF-16 code units.
    fn selection_utf16_len(&self) -> UTF16CodeUnits {
        self.fold_selection_slices(UTF16CodeUnits::zero(), |len, slice| {
            *len += UTF16CodeUnits(slice.chars().map(char::len_utf16).sum::<usize>())
        })
    }

    /// Run the callback on a series of slices that, concatenated, make up the selected text.
    ///
    /// The accumulator `acc` can be mutated by the callback, and will be returned at the end.
    fn fold_selection_slices<B, F: FnMut(&mut B, &str)>(&self, mut acc: B, mut f: F) -> B {
        if self.has_selection() {
            let (start, end) = self.sorted_selection_bounds();
            let UTF8Bytes(start_offset) = start.index;
            let UTF8Bytes(end_offset) = end.index;

            if start.line == end.line {
                f(&mut acc, &self.lines[start.line][start_offset..end_offset])
            } else {
                f(&mut acc, &self.lines[start.line][start_offset..]);
                for line in &self.lines[start.line + 1..end.line] {
                    f(&mut acc, "\n");
                    f(&mut acc, line);
                }
                f(&mut acc, "\n");
                f(&mut acc, &self.lines[end.line][..end_offset])
            }
        }

        acc
    }

    pub fn replace_selection(&mut self, insert: DOMString) {
        if !self.has_selection() {
            return;
        }

        let allowed_to_insert_count = if let Some(max_length) = self.max_length {
            let len_after_selection_replaced =
                self.utf16_len().saturating_sub(self.selection_utf16_len());
            max_length.saturating_sub(len_after_selection_replaced)
        } else {
            UTF16CodeUnits(usize::MAX)
        };

        let UTF8Bytes(last_char_index) =
            len_of_first_n_code_units(&insert, allowed_to_insert_count);
        let to_insert = &insert[..last_char_index];

        let (start, end) = self.sorted_selection_bounds();
        let UTF8Bytes(start_offset) = start.index;
        let UTF8Bytes(end_offset) = end.index;

        let new_lines = {
            let prefix = &self.lines[start.line][..start_offset];
            let suffix = &self.lines[end.line][end_offset..];
            let lines_prefix = &self.lines[..start.line];
            let lines_suffix = &self.lines[end.line + 1..];

            let mut insert_lines = if self.multiline {
                to_insert.split('\n').map(DOMString::from).collect()
            } else {
                vec![DOMString::from(to_insert)]
            };

            // FIXME(ajeffrey): efficient append for DOMStrings
            let mut new_line = prefix.to_owned();

            new_line.push_str(&insert_lines[0]);
            insert_lines[0] = DOMString::from(new_line);

            let last_insert_lines_index = insert_lines.len() - 1;
            self.edit_point.index = insert_lines[last_insert_lines_index].len_utf8();
            self.edit_point.line = start.line + last_insert_lines_index;

            // FIXME(ajeffrey): efficient append for DOMStrings
            insert_lines[last_insert_lines_index].push_str(suffix);

            let mut new_lines = vec![];
            new_lines.extend_from_slice(lines_prefix);
            new_lines.extend_from_slice(&insert_lines);
            new_lines.extend_from_slice(lines_suffix);
            new_lines
        };

        self.lines = new_lines;
        self.was_last_change_by_set_content = false;
        self.clear_selection();
        self.assert_ok_selection();
    }

    /// Return the length in bytes of the current line under the editing point.
    pub fn current_line_length(&self) -> UTF8Bytes {
        self.lines[self.edit_point.line].len_utf8()
    }

    /// Adjust the editing point position by a given number of lines. The resulting column is
    /// as close to the original column position as possible.
    pub fn adjust_vertical(&mut self, adjust: isize, select: Selection) {
        if !self.multiline {
            return;
        }

        if select == Selection::Selected {
            if self.selection_origin.is_none() {
                self.selection_origin = Some(self.edit_point);
            }
        } else {
            self.clear_selection();
        }

        assert!(self.edit_point.line < self.lines.len());

        let target_line: isize = self.edit_point.line as isize + adjust;

        if target_line < 0 {
            self.edit_point.line = 0;
            self.edit_point.index = UTF8Bytes::zero();
            if self.selection_origin.is_some() &&
                (self.selection_direction == SelectionDirection::None ||
                    self.selection_direction == SelectionDirection::Forward)
            {
                self.selection_origin = Some(TextPoint {
                    line: 0,
                    index: UTF8Bytes::zero(),
                });
            }
            return;
        } else if target_line as usize >= self.lines.len() {
            self.edit_point.line = self.lines.len() - 1;
            self.edit_point.index = self.current_line_length();
            if self.selection_origin.is_some() &&
                (self.selection_direction == SelectionDirection::Backward)
            {
                self.selection_origin = Some(self.edit_point);
            }
            return;
        }

        let UTF8Bytes(edit_index) = self.edit_point.index;
        let col = self.lines[self.edit_point.line][..edit_index]
            .chars()
            .count();
        self.edit_point.line = target_line as usize;
        // NOTE: this adjusts to the nearest complete Unicode codepoint, rather than grapheme cluster
        self.edit_point.index = len_of_first_n_chars(&self.lines[self.edit_point.line], col);
        if let Some(origin) = self.selection_origin {
            if ((self.selection_direction == SelectionDirection::None ||
                self.selection_direction == SelectionDirection::Forward) &&
                self.edit_point <= origin) ||
                (self.selection_direction == SelectionDirection::Backward &&
                    origin <= self.edit_point)
            {
                self.selection_origin = Some(self.edit_point);
            }
        }
        self.assert_ok_selection();
    }

    /// Adjust the editing point position by a given number of bytes. If the adjustment
    /// requested is larger than is available in the current line, the editing point is
    /// adjusted vertically and the process repeats with the remaining adjustment requested.
    pub fn adjust_horizontal(
        &mut self,
        adjust: UTF8Bytes,
        direction: Direction,
        select: Selection,
    ) {
        if self.adjust_selection_for_horizontal_change(direction, select) {
            return;
        }
        self.perform_horizontal_adjustment(adjust, direction, select);
    }

    /// Adjust the editing point position by exactly one grapheme cluster. If the edit point
    /// is at the beginning of the line and the direction is "Backward" or the edit point is at
    /// the end of the line and the direction is "Forward", a vertical adjustment is made
    pub fn adjust_horizontal_by_one(&mut self, direction: Direction, select: Selection) {
        if self.adjust_selection_for_horizontal_change(direction, select) {
            return;
        }
        let adjust = {
            let current_line = &self.lines[self.edit_point.line];
            let UTF8Bytes(current_offset) = self.edit_point.index;
            let next_ch = match direction {
                Direction::Forward => current_line[current_offset..].graphemes(true).next(),
                Direction::Backward => current_line[..current_offset].graphemes(true).next_back(),
            };
            match next_ch {
                Some(c) => UTF8Bytes(c.len()),
                None => UTF8Bytes::one(), // Going to the next line is a "one byte" offset
            }
        };
        self.perform_horizontal_adjustment(adjust, direction, select);
    }

    /// Return whether to cancel the caret move
    fn adjust_selection_for_horizontal_change(
        &mut self,
        adjust: Direction,
        select: Selection,
    ) -> bool {
        if select == Selection::Selected {
            if self.selection_origin.is_none() {
                self.selection_origin = Some(self.edit_point);
            }
        } else if self.has_selection() {
            self.edit_point = match adjust {
                Direction::Backward => self.selection_start(),
                Direction::Forward => self.selection_end(),
            };
            self.clear_selection();
            return true;
        }
        false
    }

    /// Update the field selection_direction.
    ///
    /// When the edit_point (or focus) is before the selection_origin (or anchor)
    /// you have a backward selection. Otherwise you have a forward selection.
    fn update_selection_direction(&mut self) {
        debug!(
            "edit_point: {:?}, selection_origin: {:?}",
            self.edit_point, self.selection_origin
        );
        self.selection_direction = if Some(self.edit_point) < self.selection_origin {
            SelectionDirection::Backward
        } else {
            SelectionDirection::Forward
        }
    }

    fn perform_horizontal_adjustment(
        &mut self,
        adjust: UTF8Bytes,
        direction: Direction,
        select: Selection,
    ) {
        match direction {
            Direction::Backward => {
                let remaining = self.edit_point.index;
                if adjust > remaining && self.edit_point.line > 0 {
                    self.adjust_vertical(-1, select);
                    self.edit_point.index = self.current_line_length();
                    // one shift is consumed by the change of line, hence the -1
                    self.adjust_horizontal(
                        adjust.saturating_sub(remaining + UTF8Bytes::one()),
                        direction,
                        select,
                    );
                } else {
                    self.edit_point.index = remaining.saturating_sub(adjust);
                }
            },
            Direction::Forward => {
                let remaining = self
                    .current_line_length()
                    .saturating_sub(self.edit_point.index);
                if adjust > remaining && self.lines.len() > self.edit_point.line + 1 {
                    self.adjust_vertical(1, select);
                    self.edit_point.index = UTF8Bytes::zero();
                    // one shift is consumed by the change of line, hence the -1
                    self.adjust_horizontal(
                        adjust.saturating_sub(remaining + UTF8Bytes::one()),
                        direction,
                        select,
                    );
                } else {
                    self.edit_point.index =
                        min(self.current_line_length(), self.edit_point.index + adjust);
                }
            },
        };
        self.update_selection_direction();
        self.assert_ok_selection();
    }

    /// Deal with a newline input.
    pub fn handle_return(&mut self) -> KeyReaction {
        if !self.multiline {
            KeyReaction::TriggerDefaultAction
        } else {
            self.insert_char('\n');
            KeyReaction::DispatchInput
        }
    }

    /// Select all text in the input control.
    pub fn select_all(&mut self) {
        self.selection_origin = Some(TextPoint {
            line: 0,
            index: UTF8Bytes::zero(),
        });
        let last_line = self.lines.len() - 1;
        self.edit_point.line = last_line;
        self.edit_point.index = self.lines[last_line].len_utf8();
        self.selection_direction = SelectionDirection::Forward;
        self.assert_ok_selection();
    }

    /// Remove the current selection.
    pub fn clear_selection(&mut self) {
        self.selection_origin = None;
        self.selection_direction = SelectionDirection::None;
    }

    /// Remove the current selection and set the edit point to the end of the content.
    pub fn clear_selection_to_limit(&mut self, direction: Direction) {
        self.clear_selection();
        self.adjust_horizontal_to_limit(direction, Selection::NotSelected);
    }

    pub fn adjust_horizontal_by_word(&mut self, direction: Direction, select: Selection) {
        if self.adjust_selection_for_horizontal_change(direction, select) {
            return;
        }
        let shift_increment: UTF8Bytes = {
            let current_index = self.edit_point.index;
            let current_line = self.edit_point.line;
            let mut newline_adjustment = UTF8Bytes::zero();
            let mut shift_temp = UTF8Bytes::zero();
            match direction {
                Direction::Backward => {
                    let input: &str;
                    if current_index == UTF8Bytes::zero() && current_line > 0 {
                        input = &self.lines[current_line - 1];
                        newline_adjustment = UTF8Bytes::one();
                    } else {
                        let UTF8Bytes(remaining) = current_index;
                        input = &self.lines[current_line][..remaining];
                    }

                    let mut iter = input.split_word_bounds().rev();
                    loop {
                        match iter.next() {
                            None => break,
                            Some(x) => {
                                shift_temp += UTF8Bytes(x.len());
                                if x.chars().any(|x| x.is_alphabetic() || x.is_numeric()) {
                                    break;
                                }
                            },
                        }
                    }
                },
                Direction::Forward => {
                    let input: &str;
                    let remaining = self.current_line_length().saturating_sub(current_index);
                    if remaining == UTF8Bytes::zero() && self.lines.len() > self.edit_point.line + 1
                    {
                        input = &self.lines[current_line + 1];
                        newline_adjustment = UTF8Bytes::one();
                    } else {
                        let UTF8Bytes(current_offset) = current_index;
                        input = &self.lines[current_line][current_offset..];
                    }

                    let mut iter = input.split_word_bounds();
                    loop {
                        match iter.next() {
                            None => break,
                            Some(x) => {
                                shift_temp += UTF8Bytes(x.len());
                                if x.chars().any(|x| x.is_alphabetic() || x.is_numeric()) {
                                    break;
                                }
                            },
                        }
                    }
                },
            };

            shift_temp + newline_adjustment
        };

        self.adjust_horizontal(shift_increment, direction, select);
    }

    pub fn adjust_horizontal_to_line_end(&mut self, direction: Direction, select: Selection) {
        if self.adjust_selection_for_horizontal_change(direction, select) {
            return;
        }
        let shift: usize = {
            let current_line = &self.lines[self.edit_point.line];
            let UTF8Bytes(current_offset) = self.edit_point.index;
            match direction {
                Direction::Backward => current_line[..current_offset].len(),
                Direction::Forward => current_line[current_offset..].len(),
            }
        };
        self.perform_horizontal_adjustment(UTF8Bytes(shift), direction, select);
    }

    pub fn adjust_horizontal_to_limit(&mut self, direction: Direction, select: Selection) {
        if self.adjust_selection_for_horizontal_change(direction, select) {
            return;
        }
        match direction {
            Direction::Backward => {
                self.edit_point.line = 0;
                self.edit_point.index = UTF8Bytes::zero();
            },
            Direction::Forward => {
                self.edit_point.line = &self.lines.len() - 1;
                self.edit_point.index = (self.lines[&self.lines.len() - 1]).len_utf8();
            },
        }
    }

    /// Process a given `KeyboardEvent` and return an action for the caller to execute.
    pub fn handle_keydown(&mut self, event: &KeyboardEvent) -> KeyReaction {
        let key = event.key();
        let mods = event.modifiers();
        self.handle_keydown_aux(key, mods, cfg!(target_os = "macos"))
    }

    // This function exists for easy unit testing.
    // To test Mac OS shortcuts on other systems a flag is passed.
    pub fn handle_keydown_aux(
        &mut self,
        key: Key,
        mut mods: Modifiers,
        macos: bool,
    ) -> KeyReaction {
        let maybe_select = if mods.contains(Modifiers::SHIFT) {
            Selection::Selected
        } else {
            Selection::NotSelected
        };
        mods.remove(Modifiers::SHIFT);
        ShortcutMatcher::new(KeyState::Down, key.clone(), mods)
            .shortcut(Modifiers::CONTROL | Modifiers::ALT, 'B', || {
                self.adjust_horizontal_by_word(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::CONTROL | Modifiers::ALT, 'F', || {
                self.adjust_horizontal_by_word(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::CONTROL | Modifiers::ALT, 'A', || {
                self.adjust_horizontal_to_line_end(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::CONTROL | Modifiers::ALT, 'E', || {
                self.adjust_horizontal_to_line_end(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::CONTROL, 'A', || {
                self.adjust_horizontal_to_line_end(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::CONTROL, 'E', || {
                self.adjust_horizontal_to_line_end(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(CMD_OR_CONTROL, 'A', || {
                self.select_all();
                KeyReaction::RedrawSelection
            })
            .shortcut(CMD_OR_CONTROL, 'X', || {
                if let Some(text) = self.get_selection_text() {
                    self.clipboard_provider.set_clipboard_contents(text);
                    self.delete_char(Direction::Backward);
                }
                KeyReaction::DispatchInput
            })
            .shortcut(CMD_OR_CONTROL, 'C', || {
                if let Some(text) = self.get_selection_text() {
                    self.clipboard_provider.set_clipboard_contents(text);
                }
                KeyReaction::DispatchInput
            })
            .shortcut(CMD_OR_CONTROL, 'V', || {
                let contents = self.clipboard_provider.clipboard_contents();
                self.insert_string(contents);
                KeyReaction::DispatchInput
            })
            .shortcut(Modifiers::empty(), Key::Delete, || {
                self.delete_char(Direction::Forward);
                KeyReaction::DispatchInput
            })
            .shortcut(Modifiers::empty(), Key::Backspace, || {
                self.delete_char(Direction::Backward);
                KeyReaction::DispatchInput
            })
            .optional_shortcut(macos, Modifiers::META, Key::ArrowLeft, || {
                self.adjust_horizontal_to_line_end(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::META, Key::ArrowRight, || {
                self.adjust_horizontal_to_line_end(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::META, Key::ArrowUp, || {
                self.adjust_horizontal_to_limit(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::META, Key::ArrowDown, || {
                self.adjust_horizontal_to_limit(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::ALT, Key::ArrowLeft, || {
                self.adjust_horizontal_by_word(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::ALT, Key::ArrowRight, || {
                self.adjust_horizontal_by_word(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::ArrowLeft, || {
                self.adjust_horizontal_by_one(Direction::Backward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::ArrowRight, || {
                self.adjust_horizontal_by_one(Direction::Forward, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::ArrowUp, || {
                self.adjust_vertical(-1, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::ArrowDown, || {
                self.adjust_vertical(1, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::Enter, || self.handle_return())
            .optional_shortcut(macos, Modifiers::empty(), Key::Home, || {
                self.edit_point.index = UTF8Bytes::zero();
                KeyReaction::RedrawSelection
            })
            .optional_shortcut(macos, Modifiers::empty(), Key::End, || {
                self.edit_point.index = self.current_line_length();
                self.assert_ok_selection();
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::PageUp, || {
                self.adjust_vertical(-28, maybe_select);
                KeyReaction::RedrawSelection
            })
            .shortcut(Modifiers::empty(), Key::PageDown, || {
                self.adjust_vertical(28, maybe_select);
                KeyReaction::RedrawSelection
            })
            .otherwise(|| {
                if let Key::Character(ref c) = key {
                    self.insert_string(c.as_str());
                    return KeyReaction::DispatchInput;
                }
                KeyReaction::Nothing
            })
            .unwrap()
    }

    pub fn handle_compositionend(&mut self, event: &CompositionEvent) -> KeyReaction {
        self.insert_string(event.data());
        KeyReaction::DispatchInput
    }

    /// Whether the content is empty.
    pub fn is_empty(&self) -> bool {
        self.lines.len() <= 1 && self.lines.get(0).map_or(true, |line| line.is_empty())
    }

    /// The length of the content in bytes.
    pub fn len_utf8(&self) -> UTF8Bytes {
        self.lines
            .iter()
            .fold(UTF8Bytes::zero(), |m, l| {
                m + l.len_utf8() + UTF8Bytes::one() // + 1 for the '\n'
            })
            .saturating_sub(UTF8Bytes::one())
    }

    /// The total number of code units required to encode the content in utf16.
    pub fn utf16_len(&self) -> UTF16CodeUnits {
        self.lines
            .iter()
            .fold(UTF16CodeUnits::zero(), |m, l| {
                m + UTF16CodeUnits(l.chars().map(char::len_utf16).sum::<usize>() + 1)
                // + 1 for the '\n'
            })
            .saturating_sub(UTF16CodeUnits::one())
    }

    /// The length of the content in Unicode code points.
    pub fn char_count(&self) -> usize {
        self.lines.iter().fold(0, |m, l| {
            m + l.chars().count() + 1 // + 1 for the '\n'
        }) - 1
    }

    /// Get the current contents of the text input. Multiple lines are joined by \n.
    pub fn get_content(&self) -> DOMString {
        let mut content = "".to_owned();
        for (i, line) in self.lines.iter().enumerate() {
            content.push_str(line);
            if i < self.lines.len() - 1 {
                content.push('\n');
            }
        }
        DOMString::from(content)
    }

    /// Get a reference to the contents of a single-line text input. Panics if self is a multiline input.
    pub fn single_line_content(&self) -> &DOMString {
        assert!(!self.multiline);
        &self.lines[0]
    }

    /// Set the current contents of the text input. If this is control supports multiple lines,
    /// any \n encountered will be stripped and force a new logical line.
    pub fn set_content(&mut self, content: DOMString) {
        self.lines = if self.multiline {
            // https://html.spec.whatwg.org/multipage/#textarea-line-break-normalisation-transformation
            content
                .replace("\r\n", "\n")
                .split(|c| c == '\n' || c == '\r')
                .map(DOMString::from)
                .collect()
        } else {
            vec![content]
        };

        self.was_last_change_by_set_content = true;
        self.edit_point = self.edit_point.constrain_to(&self.lines);

        if let Some(origin) = self.selection_origin {
            self.selection_origin = Some(origin.constrain_to(&self.lines));
        }
        self.assert_ok_selection();
    }

    /// Convert a TextPoint into a byte offset from the start of the content.
    fn text_point_to_offset(&self, text_point: &TextPoint) -> UTF8Bytes {
        self.lines
            .iter()
            .enumerate()
            .fold(UTF8Bytes::zero(), |acc, (i, val)| {
                if i < text_point.line {
                    acc + val.len_utf8() + UTF8Bytes::one() // +1 for the \n
                } else {
                    acc
                }
            }) +
            text_point.index
    }

    /// Convert a byte offset from the start of the content into a TextPoint.
    fn offset_to_text_point(&self, abs_point: UTF8Bytes) -> TextPoint {
        let mut index = abs_point;
        let mut line = 0;
        let last_line_idx = self.lines.len() - 1;
        self.lines
            .iter()
            .enumerate()
            .fold(UTF8Bytes::zero(), |acc, (i, val)| {
                if i != last_line_idx {
                    let line_end = val.len_utf8();
                    let new_acc = acc + line_end + UTF8Bytes::one();
                    if abs_point >= new_acc && index > line_end {
                        index = index.saturating_sub(line_end + UTF8Bytes::one());
                        line += 1;
                    }
                    new_acc
                } else {
                    acc
                }
            });

        TextPoint { line, index }
    }

    pub fn set_selection_range(&mut self, start: u32, end: u32, direction: SelectionDirection) {
        let mut start = UTF8Bytes(start as usize);
        let mut end = UTF8Bytes(end as usize);
        let text_end = self.get_content().len_utf8();

        if end > text_end {
            end = text_end;
        }
        if start > end {
            start = end;
        }

        self.selection_direction = direction;

        match direction {
            SelectionDirection::None | SelectionDirection::Forward => {
                self.selection_origin = Some(self.offset_to_text_point(start));
                self.edit_point = self.offset_to_text_point(end);
            },
            SelectionDirection::Backward => {
                self.selection_origin = Some(self.offset_to_text_point(end));
                self.edit_point = self.offset_to_text_point(start);
            },
        }
        self.assert_ok_selection();
    }

    /// Set the edit point index position based off of a given grapheme cluster offset
    pub fn set_edit_point_index(&mut self, index: usize) {
        let byte_offset = self.lines[self.edit_point.line]
            .graphemes(true)
            .take(index)
            .fold(UTF8Bytes::zero(), |acc, x| acc + x.len_utf8());
        self.edit_point.index = byte_offset;
    }
}